1. Field of the Invention
The present invention relates generally to fluid-filled vibration-damping devices exhibiting vibration damping effect on the basis of flows of non-compressible fluid filled therein. More particularly, the present invention is concerned with such a fluid-filled vibration-damping device that is novel in construction, and that is capable of providing an improved fluid-tight sealing without deteriorating efficiency in assembling and manufacturing the fluid-filled vibration-damping device.
2. Description of the Related Art
A fluid-filled vibration-damping device is known as one type of a vibration damping device interposed between two members of a vibration system for elastically connecting the two members, or for mounting one of the two members of the vibration system on the other member in a vibration damping fashion. JP-A-8-291844, JP-A-2001-59540 and JP-A-10-38016 disclose known examples of such a fluid-filled vibration-damping device, which includes a first mounting member adapted to be attached to one of the two members of the vibration system, a second mounting member adapted to be attached to the other member of the vibration system, and a rubber elastic body that is bonded at its central portion to the first mounting member and at its outer circumferential portion to the second mounting member for elastically connecting the first and second mounting members. The rubber elastic body partially defines a pressure-receiving chamber on one of opposite-side thereof. The pressure-receiving chamber is filled with the non-compressible fluid and adapted to receive vibrational load applied to the fluid-filled vibration-damping device. On the other side of the rubber elastic body, a flexible diaphragm formed of a rubber material is disposed so as to extend between the first and second mounting members, whereby the rubber elastic body and the flexible diaphragm cooperate to define therebetween an equilibrium chamber partially defined by the flexible diaphragm. The equilibrium chamber is filled with the non-compressible fluid, and has a volume that is variable due to deformation of the flexible diaphragm. The fluid-filled vibration-damping device further includes an first orifice passage for a fluid communication between the pressure-receiving chamber and the equilibrium chamber.
For the sake of efficiency in manufacture, the known fluid-filled vibration-damping device as disclosed in the aforesaid publication documents is arranged such that the rubber elastic body and the flexible diaphragm are formed independently from each other, and the rubber elastic body is bonded at its central portion to a central metal member for the rubber elastic body (hereinafter referred to as an “elastic-body central metal member”), while the flexible diaphragm is bonded at its central portion to a central metal member for the flexible diaphragm (hereinafter referred to as a “diaphragm central metal member”). These elastic-body and diaphragm central metal members are superposed on and fixed to each other, thereby providing the first mounting member.
However, as shown in the aforementioned JP-A-2001-59540 and JP-A-10-38016, for example, the conventional fluid-filled vibration-damping device is likely to suffer from a problem of leakage of the fluid originated in its structural feature. Namely, the elastic-body central metal member is provided with a fixing bolt protruding therefrom at which the first mounting member is fixed to one of the two members connected together in the vibration-damping fashion. On the other hand, the diaphragm central metal member is provided with a through hole formed through its central portion. These elastic-body and diaphragm central metal members are superposed on each other with the fixing bolt of the elastic body central metal member extending through the through hole of the diaphragm central portion. Consequently, an interface between the elastic-body central metal member and the diaphragm central metal member are substantially directly exposed to the atmosphere at the through hole portion of the diaphragm central metal member. Since an outer peripheral portion of the interface between the elastic-body central metal member and the diaphragm central metal member faces to the equilibrium chamber, the non-compressible fluid filling the equilibrium chamber is likely to be leaked out through the interface and the through hole of the diaphragm central metal member. In this respect, it should be noted that the fluid-filled vibration-damping device disclosed in the above described JP-A-8-291844 also suffers from the same inherent problem, although a clear depiction of the through hole formed through the diaphragm central metal member is just omitted.
In the conventional fluid-filled vibration-damping devices shown in the above-described publication documents, moreover, the elastic-body central metal member and the diaphragm central metal member are just superposed on each other at their plane abutting surfaces, in order to constitute the first mounting member. This arrangement makes it difficult to precisely position the two central metal members relative to each other upon assembling these two members together, and may possibly cause displacement of the two central metal members relative to each other, leading to undesirable leakage of the non-compressible fluid through the interface between abutting surfaces of the two central metal members.
Also, the diaphragm central metal member is not directly fixed to the elastic-body central metal member, but is just gripped by and between the elastic-body central metal member and the one member of the two members connected together in the vibration damping fashion, to which the elastic-body central metal member is bolted. This conventional structure is likely to cause looseness between the elastic-body central metal member and the diaphragm central metal member due to an effect of the vibrations applied thereto, resulting in difficulty in assuring a high fluid-tight sealing at the interface between the two central metal members with high stability.
JP-A-9-257090 discloses an example of modification of the above-described fluid-filled vibration-damping device proposed in an attempt to cope with the above-described conventional problem, in which the elastic body and the flexible diaphragm are formed as components of an integral vulcanized products. However, it is difficult in view of the shape or structure of a mold for forming the integral vulcanized product including the elastic body and the flexible diaphragm as the components. Further, such an integral vulcanized product makes it impossible to select suitable materials for the elastic body and the flexible diaphragm, respectively, in the light of required characteristics of the respective ones. For the above reasons, the proposed modification is not sufficient to solve the conventional problem.